CN102721864B - System and method for time-staggered acquisition of high-frequency electric-arc signal - Google Patents

Abstract

The invention discloses a high-frequency arc signal time-staggered acquisition system and method, relating to the field of welding control. The system includes a spectrometer, a high-speed camera, a voltage sensor, a current sensor, a touch screen, a serial communication circuit, an MCU controller, an isolation circuit, a signal amplification circuit, a power supply circuit, and a signal acquisition circuit; wherein the MCU controller is used as a main control device through the serial port The communication circuit and HMI communication set the number of sampling points per cycle N, and the arc signal collected by the current sensor and voltage sensor is input to the MCU controller through the signal acquisition circuit for analysis and processing; the PWM signal sent by the MCU controller is controlled by the isolation circuit and signal amplification output. Spectrometer and high-speed camera; using a voltage comparator to directly convert the target signal into a square wave is equivalent to directly obtaining its signal frequency, which can be used to collect high-frequency arc signals, avoiding errors caused by measurement and collection, and has high accuracy.

Description

System and method for time-staggered acquisition of high-frequency arc signals

technical field

The invention provides a high-frequency arc signal time-staggered acquisition system and method, which relate to the field of welding control.

Background technique

Pulse TIG welding has unique advantages in improving energy density, heat input control, weld seam shape memory welding quality, etc., and has been widely used in manufacturing in recent years. But the current application frequency of pulsed arc is generally below 30KHz. A further increase in frequency will affect the authenticity of arc signal acquisition and cause great difficulties.

Contents of the invention

In order to realize the problem of high-frequency signal collection, the present invention adopts a time-staggered collection method, collects multiple points in multiple cycles, and then integrates them into a complete cycle to reflect the real situation. The specific implementation plan is as follows:

High-frequency arc signal time-staggered acquisition system: including spectrometer, high-speed camera, voltage sensor, current sensor, touch screen, serial communication circuit, MCU controller, isolation circuit, signal amplification circuit, power supply circuit, and signal acquisition circuit. The MCU controller is the main The control device communicates with the HMI through the serial port communication circuit to set the number of sampling points per cycle N, and the arc signals collected by the current sensor and voltage sensor are input to the MCU controller through the signal acquisition circuit for analysis and processing. The PWM signal sent by the MCU controller controls the spectrometer and high-speed camera through the isolation circuit and signal amplification output.

Signal acquisition circuit: The input terminal of the signal acquisition circuit inputs the high-frequency signal collected from the welding equipment by the Hall current sensor, and then enters the MUC controller after passing through the comparator U6.

In the isolation circuit, the 4 PWM signals sent by the MCU controller are respectively output through the high-speed optocoupler O1, high-speed optocoupler O2, high-speed optocoupler O3, and high-speed optocoupler O4. The independent power supply of the isolation circuit is formed by connecting the output port of the power chip 7805 of the power circuit to the DC-DC chip U8 and then connecting the rectifier chip U7 and a current circuit composed of capacitors.

The signal amplifying circuit, the PWM signal outputted by the high-speed optocoupler O1, the high-speed optocoupler O2, the high-speed optocoupler O3, and the high-speed optocoupler O4 is connected to the comparator U9 for signal amplification and then output.

The power supply circuit is composed of an external power supply, a rectifier chip U1 and a rectifier chip U2, and resistors and capacitors.

The serial port communication circuit, the serial port communication signal output by the MCU controller is connected to the serial port connector for output after passing through the RS232 communication interface chip U4.

The MCU controller adopts a 32-bit CortexM3 microprocessor based on the ARM core of the model STM32F103RBT6.

A high-frequency arc signal acquisition method, as shown in Figure 1: Step 1: The voltage sensor and the current sensor input the arc signal collected by the signal acquisition circuit as the input signal of the voltage comparator U6, and the output signal of the voltage comparator U6 In order to synchronize the square wave signal with the same period as T1 with the input signal, obtain the period of the signal to be tested. The output signal of the voltage comparator U6 is input to the MCU controller as the base frequency signal. Step 2: Set the number of sampling points per cycle N in the program through the touch screen, then ∆t=T1/N, and input it to the MCU controller through the serial port communication circuit. Step 3: The MCU controller obtains the period T1 of the square wave signal output by the voltage comparator U6, and then outputs a PWM signal with a period T2. The relationship between the two is T2=n×T1+∆t. The PWM signal output by the MCU controller is output as the driving signal of the spectrometer and high-speed camera through the isolation circuit and the amplification circuit. The spectrometer and high-speed camera collect the arc signal on the rising edge of the PWM signal. The complete cycle information of the signal to be tested can be obtained by superimposing the collected image information.

Among them: T1 is the period of the input signal, N is the number of sampling points per cycle of the signal, T2 is the period of the PWM signal output by the MCU controller, and ∆t is the interval between every two adjacent sampling points.

The invention uses a voltage comparator to realize the frequency acquisition of the signal to be tested, and inputs the square wave signal with the same period T1 as the signal to be tested into the MCU. The target PWM whose period is T2 is used as the acquisition trigger signal by the software. Using a voltage comparator to directly convert the target signal into a square wave is equivalent to directly obtaining its signal frequency, which can be used to collect high-frequency arc signals, avoiding errors caused by measurement and collection, and has high accuracy.

Description of drawings

Figure 1. Schematic diagram of time-staggered collection method;

Fig. 2. schematic block diagram of the present invention;

Fig. 3. MCU control circuit of the present invention;

Fig. 4. the serial port communication circuit of the present invention;

Figure 5. Signal acquisition circuit;

Figure 6. Isolation circuit;

Figure 7. Signal amplification circuit;

Figure 8. Power supply circuit;

Figure 9. Isolated part of the power supply circuit;

Fig. 10. method flowchart of the present invention;

Detailed ways

Specific embodiments of the present invention The present invention will be described in detail with reference to the accompanying drawings.

The system is mainly composed of HMI, serial communication circuit, MCU controller, isolation circuit, operational amplifier circuit, power supply circuit, spectrometer, high-speed camera, voltage sensor, and current sensor.

As shown in Figure 2, the power supply circuit supplies power to the entire circuit board, and the signal isolation between the control signal of the MCU and the signal amplification and filtering circuit, and between the input signal and the MCU is realized by an isolation circuit. When the system is working, the input signal is compared with the reference voltage of the voltage comparator to output a pulse signal with the same frequency as the input signal and cut synchronously, and input it into the MCU. The operator sets the PWM duty ratio and frequency required by the signal acquisition system through the HMI. The HMI and the MCU controller are connected through a serial communication circuit. Add a period of delay on the basis of a fixed frequency and then output a PWM signal with a corresponding duty cycle and frequency, which is used to drive signal acquisition equipment such as a spectrometer. It is equivalent to collecting signals at different positions in the same cycle. The purpose of collecting high-frequency signals at staggered times is achieved.

Fig. 3 is the MCU part of the present invention, USART_TX, USART_RX are the serial port communication pins, respectively connected with U4 to realize the serial port communication. PWM1-4 are PWM signal output pins, which are respectively connected to pins 1-4 of U8. The crystal oscillator Y1 and the start-up capacitors at both ends are used together to provide a clock source for the system. Pin 37 of the MCU is a square wave signal input pin.

Fig. 4 is the serial port communication circuit of the present invention, the required PWM frequency and the number of sampling points are input by the HMI, and sent to the MCU through the serial port communication to complete the setting of the target PWM. U4 (232 chip) connects HMI and MCU. U4 realizes the serial port communication between HMI and MCU through level conversion based on 232 standard.

Figure 5 is a circuit diagram of the signal acquisition part, as shown in the figure, the external signal is connected to U6A through terminal P2, U6A and R4 form a voltage follower, the output voltage of the voltage follower is similar to the input voltage range, and presents a high resistance to the previous circuit state, it is in a low-impedance state for the subsequent stage circuit, and thus plays an isolation role for the front and rear stage circuits. U6B, R5 and R6 form a zero-crossing comparator, which converts the irregular arc signal into a square wave signal with the same frequency.

Figure 6 is an isolation circuit, and the output part of the control signal adopts a high-speed optocoupler output. The PWM signal is respectively input to the input end of the optocoupler of each PWM output channel through U8, in which U8 plays the role of amplifying the PWM signal, which improves the driving ability of the signal and enables better driving of the optocoupler, and the use of the optocoupler realizes isolated output of the signal.

Figure 7 is an operational amplifier circuit. As shown in the figure, the positive-phase input terminals of the four operational amplifiers A, B, C, and D of U9 are respectively connected to the output of the control signal PWM1-4. The PWM signal is amplified by the operational amplifier three times and then output to respective terminal pins. The U9 power supply comes from DC-DC, (explain in the power supply section).

Figure 8 is the circuit diagram of the power supply part of the system. The terminal P1 is input with 9V DC power from the outside, filtered by the capacitor, and then the current-limiting resistor R1 is input to the power conversion chip U1, and the output is 5V power. The power conversion chip U2 also outputs 3.3V power. supply power to all parts of the system.

Figure 9 is a schematic diagram of the isolated part of the power supply. The DC-DC input terminal power is taken from U1, and the output is 15V power supply for U9. The input terminal of the U7 power conversion chip is taken from the DC-DC output terminal 15V power supply, and U7 outputs 5V power supply for high-speed The collector of the optocoupler supplies power. In this way, the external equipment and the system are fully isolated by using optocouplers. The part connecting the optocoupler and the system is powered by the system power supply, and the part connecting the optocoupler and the external equipment is powered by the DC-DC output power supply, which fully protects the safety of the system.

In the present invention, the MCU controller expands the 232 bus interface, which can communicate with the HMI. On the HMI, you can set the PWM duty cycle and frequency and display the received data in real time.

In this embodiment, the high-frequency arc signal staggered acquisition method is schematically shown in Figure 1: the first step: the voltage sensor and the current sensor input the arc signal that is collected into the signal acquisition circuit as the input signal of the voltage comparator U6, and the voltage sensor of the voltage comparator U6 The output signal is a square wave signal with the same cycle as T1 synchronously with the input signal, and the cycle of the signal to be tested is obtained. The output signal of the voltage comparator U6 is input to the MCU controller as the base frequency signal. Step 2: Set the number of sampling points per cycle N in the program through the touch screen, then ∆t=T1/N, and input it to the MCU controller through the serial port communication circuit. Step 3: The MCU controller obtains the period T1 of the square wave signal output by the voltage comparator U6, and then outputs a PWM signal with a period T2. The relationship between the two is T2=n×T1+∆t. The PWM signal output by the MCU controller is output as the driving signal of the spectrometer and high-speed camera through the isolation circuit and the amplification circuit. The spectrometer and high-speed camera collect the arc signal on the rising edge of the PWM signal. The complete cycle information of the signal to be tested can be obtained by superimposing the collected image information.

Among them: T1 is the period of the input signal, N is the number of sampling points per cycle of the signal, T2 is the period of the PWM signal output by the MCU controller, and ∆t is the interval between every two adjacent sampling points.

Claims (3)

1. hf electric arc signal is staggered the time acquisition system, it is characterized in that: it comprises spectrometer, high-speed camera, voltage sensor, current sensor, touch-screen, serial communication circuit, MCU controller, buffer circuit, signal amplification circuit, power circuit, signal acquisition circuit; Wherein MCU controller is as main control equipment by serial communication circuit and HMI communications setting each cycle sampling number N, and the arc signal that current sensor, voltage sensor collect then carries out analyzing and processing by signal acquisition circuit input MCU controller; The pwm signal that MCU controller sends controls spectrometer and high-speed camera by the output of buffer circuit and signal amplification circuit;

Signal acquisition circuit: the high-frequency signal that the input end input of signal acquisition circuit is gathered from welding gear by Hall current sensor, is then input to MCU controller after comparer U6;

Buffer circuit, the 4 road pwm signals that MCU controller sends, export respectively after high speed photo coupling O1, high speed photo coupling O2, high speed photo coupling O3, high speed photo coupling O4; The independent current source of buffer circuit connects the current circuit that rectification chip U7 and electric capacity forms again and forms after connecting DC ?DC chip U8 by the delivery outlet of the power supply chip 7805 of power circuit;

Signal amplification circuit, exports after the pwm signal exported access comparer U9 carries out signal amplification after described high speed photo coupling O1, high speed photo coupling O2, high speed photo coupling O3, high speed photo coupling O4;

Power circuit, power circuit is made up of external power source and rectification chip U1 and rectification chip U2 and resistance capacitance;

Serial communication circuit, the serial communication signal that MCU controller exports is connected to serial ports joint and exports after RS232 communication interface chip U4.

2. hf electric arc signal according to claim 1 is staggered the time acquisition system, it is characterized in that: described MCU controller adopts model to be 32 Cortex M3 microprocessors based on ARM kernel of STM32F103RBT6.

3. a hf electric arc signal is staggered the time acquisition method, it is characterized in that: the first step: voltage sensor and current sensor are using the arc signal input signal Acquisition Circuit that the collects input signal as voltage comparator U6, the output signal of voltage comparator U6 is the same cycle synchronous with input signal is the square-wave signal of T1, obtains the cycle of measured signal; MCU controller is inputted using the output signal of voltage comparator U6 as fundamental frequency signal; Second step: by each cycle sampling number N in touch-screen setting program, then have Δ t=T1/N, and be input to MCU controller by serial communication circuit; 3rd step: the cycle T 1 rear output cycle that MCU controller obtains the square-wave signal that voltage comparator U6 exports is the pwm signal of T2, and the relationship of the two is T2=n × T1+ Δ t; The pwm signal that MCU controller exports exports the drive singal as spectrometer and high-speed camera by buffer circuit and amplifying circuit; Spectrometer, high-speed camera gather arc signal at the rising edge of pwm signal; The image information gathering gained is superposed, just can obtain the complete cycle information of measured signal;

Wherein: T1 is input signal cycle, N is the sampling number of signal each cycle, the pwm signal cycle that T2 exports for MCU controller, and Δ t is every two adjacent sampled point interval times.